广东平远花岗岩风化壳及其稀土成矿特征

The Weathering Crust and REE Metallogenic Characteristics of Granite in Pingyuan,Guangdong

以竹细塘和神背岩体为例，研究燕山晚期黑云母花岗岩的风化在及其稀土成矿特征，结果表明：风化壳剖面发育层状结构，自下而上，碎屑矿物减少，粘土矿物含量增加，活动组分（Ｋ＿２Ｏ，Ｎａ＿２Ｏ，ＣａＯ）减少，稳定组分（Ａｌ＿２Ｏ＿３，Ｆｅ＿２Ｏ＿３，ＴｉＯ＿２）增加．风化壳中稀土分布总体上保持原岩特征，但各风化壳层中铈负异常均增加，铕和铒负异常消失乃至出现正异常；全风化壳的中下部稀土最为富集，稀土分布型式也变化最大；在全风化和半风化壳层中稀土含量与粘土矿物呈明显的正相关关系，非矿物相稀土在风化壳中主要以活性态存在，此外还以铁铝共沉淀态和有机结合态形式赋存。

The weathering crust of late Yanshanian granite developed layered structures.Fromthe lower to the upper layer of the crust,the cot1tents of Clastic minerals and active components(K_2O ,Na_2O,CaO)decrease,while the contents of clay minerals and stable components (Al_2O_3,Fe_2O_3,TiO_2)increase,The REE distribution patterns of the weathering crust are similar to thoseof the original rocks. But the Ce negative anomaly in the weathering crust is more intense and thenegative anomaly of Eu and Er disappears or even changes to positive anomaly, The REEs aremostly accumulated in the middle to lower part of the complete weathering layer. The content ofREE has a positive relationship with that of clay minerals in the complete and medium weatheringlayers.In addition to REE-bearing minerals,the existing states of REE in the weathering crustare the active state, the Fe-Al co-precipitation state and the organic combination state.